WWW.ARBORSCI.COM
Inertia Apparatus
P3-3524
BACKGROUND:
Demonstrate inertia and Newton’s First Law in a memorable way!
This classic apparatus is standard for a reason – it works and it’s impressive! Rest the ball on top of
the square that is set on the vertical post. Release the spring and the square is projected out. The
ball falls into place on the post, remaining at rest as if nothing happened.
WHAT IS NEWTON'S FIRST LAW (LAW OF INERTIA):
Newton's first law in everyday terms is… ¬An object at rest will stay at rest, forever, as long as
nothing pushes or pulls on it. An object in motion will stay in motion, traveling in a straight line,
forever, until something pushes or pulls on it.
Scientists use the term inertia to describe this tendency of an object to resist a change in its motion.
The Latin root for Inertia means “lacking the ability to move”. So you can see how scientists came up
with the word. What's more amazing is that they came up with the concept. Inertia isn't an
immediately apparent physical property, such as length or volume. It is, however, directly related to
an object's mass. Newton wasn't the first scientist to come up with the Law of Inertia; it was Galileo
and René Descartes, but we give Newton the credit.
When demonstrating Newton’s 1st Law with this device, place the plastic square on the post,
centering the post in the middle of the square. Now place the red ball so that the flattened area
rests over the post center. Pull back the metal spring and release. The plastic square will be
projected away and the red ball will remain on the post. Why? The faster the plastic square is
moved from beneath the ball, the less tendency for friction to act on the ball, altering its position in
any way. You might experiment by placing less tension on the spring and have the plastic square
released at a slower speed. Notice what happens to the ball.
PO Box 2750
ANN ARBOR, MI 48106 T 800-367-6695
WWW.ARBORSCI.COM
©2009 ARBOR SCIENTIFIC ALL RIGHTS RESERVED
This demonstration is a great analogy to the classic “pull the tablecloth from beneath the dishes”
trick only safer! The ball’s inertia allowed it to remain at rest while the plastic square moved beneath
the ball. Remember, object’s at rest will remain at rest unless affected by an external force…
Newton’s 1st Law!
PO Box 2750
ANN ARBOR, MI 48106 T 800-367-6695
WWW.ARBORSCI.COM
©2009 ARBOR SCIENTIFIC ALL RIGHTS RESERVED